Patent GB-663527-A (GB)
Title: Improvements in and relating to electrical ignition systems
Inventor: DEBENHAM WILLIAM RICHARD
IPC: F02P1/08
Filed: 1948-03-10
Abstract: 663,527. Ignition systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Sept. 4, 1948 [March 10, 1948; May 27, 1948; July 5, 19481, Nos. 7344/48, 14389/48 and 18033/48. Class 7(iv) [Also in Group XXXV] In an electrical ignition apparatus, e.g. for gas turbine or jet type engines, cabin heaters, flame warfare apparatus, and fog dispersal apparatus, in which a charge accumulating condenser is connected to receive via a relatively high voltage two electrode " charging spark gap repeated unidirectional charges from an induction coil and to discharge when the voltage of the accumulated charge thereon is suffi- . ciently high, via a relatively low voltage discharging spark gap and a spark plug, means are provided to reduce the interelectrode voltage of the charging gap, and ensure its rapid extinction or suppression. each time the induction coil voltage declines and/or changes polarity, and thus to prevent or reduce the opportunity for discharge of the charge accumulating condenser reversely through the charging gap. The charge accumulating condenser 19, Fig. 1, is charged by the secondary winding 11 of the induction coil 11, 12 through a variable resistor 26, a high voltage spark gap 18, and an inductance 27. The condenser 19 discharges at a predetermined voltage through a low voltage sparking gap 20 and an ignition sparking plug 21. An auxiliary condenser 24 together with a series resistance 25 are connected across the coil 11 and have such values as to reduce the reverse voltages, developed in the winding 11 in the intervals between the charging pulses, sufficiently to ensure rapid extinction and suppression of the gap 18. The spark plug 21 is shunted by a resistor 22 which reduced the minimum voltage required to produce a spark. The resistance 22 can be comprised by the deposit applied to the surface of the insulation over which the duces the minimum voltage required to discharge takes place in a surface type spark plug as described in Specification 663.528. A multiple switch may be included in the spark plug lead so that a series of engines may be. started in succession. In a modified circuit the resistance 25 is connected in series with the charging circuit of the charge accumulating condenser 19, and the inductance 27 is disposed between the sparking gap 20 and the plug 21. Two further systems are described in which the discharge at the plug 21 may be initiated at a voltage higher than that of the maximum voltage of the charge accumulating condenser 19 and maintained by the charge of that condenser. A third spark gap is connected between the junction of the condenser 24 and the resistor 25 and either to the junction of two small inductances in the discharge circuit of the system, or in series with a primary winding of a stepup transformer, the secondary winding of which is connected in the discharge circuit. The first Provisional Specification describes alternative circuits in which the suppression of the charging gap 18 is effected by connecting the condenser 24 and series resistance 25 in shunt therewith.